This invention relates to rotary mowers and more particularly, to a rotary mower having improved spindle means including an automatic braking mechanism for stopping the rotation of the blade when the input power is cut off.
In mowers of the walk behind type, the cutting blade is generally attached directly to the engine mounted thereon. Consequently, when the engine is stopped, the blade stops. Mowers of the type used on garden tractors and riding mowers, however, are generally belt driven from the engine. The belt drive usually is provided with a clutch idler pulley which tensions the drive belt to drive the mower thus permitting the garden tractor or riding mower to be driven without engaging the mower. When the drive is declutched, however, the mower blade acts as a flywheel and may continue to rotate silently for a period of time after the power is shut off, leaving a potential source of injury for the person who may reach within the mower housing after declutching the engine to clear a blockage.
Various people have attacked this problem using audible warning mechanisms, such as an overrunning clutch; however, such devices do not stop the blade and probably extend the period of rotation. Others have developed mechanical braking devices such as the clutch-brake devices described in U.S. Pat. No. 3,837,450 to Malion et al. and U.S. Pat. No. 2,985,992 to Dowdle. These devices require external actuation and means for declutching the drive as well as means for braking, rendering them less useful for tractor mounted mowers.
Still others have developed automatic mower spindle brake mechanisms. U.S. Pat. No. 3,722,642 to Zurek et al. and U.S. Pat. No. 3,731,472 to Kamlukin describe similar mechanisms wherein the input sheave is threaded on the output shaft. Drive through the input sheave rotates it up the threads to a stop producing a driving coupling with the output shaft. When the mower blade overruns the input sheave due to their different inertias, reverse relative rotation occurs between the input sheave and the output shaft and the input sheave rotates downwardly on the output shaft threads to engage complemental braking surfaces on the sheave and spindle support sleeve. While these devices perform their intended function, it is found that the threaded connection between the input sheave and the output shaft tends to make the device more expensive and create wear problems. The wear problems are believed to be caused by the rocking action of the sheave on the shaft threads due to the offset nature of the loading on the input sheave. This rocking action also can cause some vibration and noise in the spindle assembly. Moreover, since the input sheave must be external of the support sleeve, sealing of the unit is difficult and the up and down movement of the sheave on the output shaft tends to pump the lubricant out of the mechanism creating further wear problems.
Accordingly, it is a general object of the invention described herein to produce a rotary mower having a relatively inexpensive blade spindle assembly which may be automatically braked upon cessation of the input drive thereto and which is less subject to wear problems.
It is a more specific object of the invention to provide an improved automatic braking means for a mower spindle assembly wherein the driving force is transferred to the output shaft independently of the braking member.
It is a further object of the invention to provide an improved mower having an automatic braking spindle assembly which is more readily adaptable to being sealed.